Tau Be or not Tau Be? - A Perspective on Service Compatibility and Substitutability

One of the main open research issues in Service Oriented Computing is to propose automated techniques to analyse service interfaces. A first problem, called compatibility, aims at determining whether a set of services (two in this paper) can be composed together and interact with each other as expected. Another related problem is to check the substitutability of one service with another. These problems are especially difficult when behavioural descriptions (i.e., message calls and their ordering) are taken into account in service interfaces. Interfaces should capture as faithfully as possible the service behaviour to make their automated analysis possible while not exhibiting implementation details. In this position paper, we choose Labelled Transition Systems to specify the behavioural part of service interfaces. In particular, we show that internal behaviours (tau transitions) are necessary in these transition systems in order to detect subtle errors that may occur when composing a set of services together. We also show that tau transitions should be handled differently in the compatibility and substitutability problem: the former problem requires to check if the compatibility is preserved every time a tau transition is traversed in one interface, whereas the latter requires a precise analysis of tau branchings in order to make the substitution preserve the properties (e.g., a compatibility notion) which were ensured before replacement.Comment: In Proceedings WCSI 2010, arXiv:1010.233

Genotoxic Effects in Swimmers Exposed to Disinfection By-products in Indoor Swimming Pools

37 páginas, 1 figura, 4 tablas.-- PDF con material suplementario.[BACKGROUND]: Exposure to disinfection by-products (DBPs) in drinking water has been associated with cancer risk. A recent study found an increased bladder cancer risk among subjects attending swimming pools relative to those not attending.[OBJECTIVES]: To evaluate whether swimming in pools is associated with biomarkers of genotoxicity.[METHODS]: We collected blood, urine, and exhaled air samples from 49 non-smoking adult volunteers before and after they swam for 40 min in an indoor chlorinated pool. We estimated associations between the concentrations of four trihalomethanes in exhaled breath and changes in the following biomarkers: micronuclei and DNA damage (comet assay) in peripheral blood lymphocytes before and 1 h after swimming, urine mutagenicity (Ames assay) before and 2 h after swimming, and micronuclei in exfoliated urothelial cells before and 2 weeks after swimming. We also estimated associations and interactions with polymorphisms in genes related to DNA repair or DBP metabolism.[RESULTS]: After swimming, the total concentration of the four trihalomethanes in exhaled breath was seven times higher than before swimming. The change in the frequency of micronucleated lymphocytes after swimming increased in association with exhaled concentrations of the brominated trihalomethanes (p = 0.03 for CHCl2Br, p = 0.05 for CHClBr2, p = 0.01 for CHBr3) but not chloroform. Swimming was not associated with DNA damage detectable by the comet assay. Urine mutagenicity increased significantly after swimming in association with the concentration of exhaled CHBr3 (p = 0.004). No significant associations with changes in micronucleated urothelial cells were observed.[CONCLUSIONS]: Our findings support potential genotoxic effects of exposure to DBPs from swimming pools. The positive health effects gained by swimming could be increased by reducing the potential health risks of pool water.Research supported by Plan Nacional Grant SAF2005-07643-C03-01/02/03, Spain and FIS CP06/00341, Spain. CM Villanueva supported by the ISCIII (CP06/00341), Spain, L Font-Ribera by a predoctoral fellowship (FI06/00651), Spain, and D Liviac by a postgraduate fellowship UAB (PIF409-009), Barcelona.Peer reviewe

The Salmonella Mutagenicity Assay: The Stethoscope of Genetic Toxicology for the 21st Century

Objectives: According to the 2007 National Research Council report Toxicology for the Twenty-First Century, modern methods (e.g., "omics," in vitro assays, high-throughput testing, computational methods) will lead to the emergence of a new approach to toxicology. The Salmonella mammalian microsome mutagenicity assay has been central to the field of genetic toxicology since the 1970s. Here we document the paradigm shifts engendered by the assay, the validation and applications of the assay, and how the assay is a model for future in vitro toxicology assays. Data sources: We searched PubMed, Scopus, and Web of Knowledge using key words relevant to the Salmonella assay and additional genotoxicity assays. Data extraction: We merged the citations, removing duplicates, and categorized the papers by year and topic. Data synthesis: The Salmonella assay led to two paradigm shifts: that some carcinogens were mutagens and that some environmental samples (e.g., air, water, soil, food, combustion emissions) were mutagenic. Although there are > 10,000 publications on the Salmonella assay, covering tens of thousands of agents, data on even more agents probably exist in unpublished form, largely as proprietary studies by industry. The Salmonella assay is a model for the development of 21st century in vitro toxicology assays in terms of the establishment of standard procedures, ability to test various agents, transferability across laboratories, validation and testing, and structure-activity analysis. Conclusions: Similar to a stethoscope as a first-line, inexpensive tool in medicine, the Salmonella assay can serve a similar, indispensable role in the foreseeable future of 21st century toxicology

Genotoxicity of urban air pollutants in the Czech Republic. Part II. DNA adduct formation in mammalian cells by extractable organic matter.

The study was aimed at determining the genotoxic potential of extractable organic matter (EOM) from ambient air particles PM10 (<10 micrometer) using mammalian cells in culture as test system. Air samples were collected in the course of summer and winter periods in two regions of the Czech Republic representing low and high levels of air pollution, the districts of industrial Teplice and rural Prachatice, respectively. EOM was fractionated by acid-base partitioning and silica gel column chromatography. Aliquots of fractions were incubated with cultured hepatocytes derived from male rats or Chinese hamster lung V79NH cells expressing nitroreductase activity but virtually no cytochrome P450 activity. DNA adduct levels were analyzed by 32P-postlabeling using butanol extraction for adduct enrichment. In hepatocytes, crude extracts caused the formation of substantial amounts of DNA reactive material being detectable in a broad diagonal radioactive zone (DRZ) in the chromatograms. Highest DNA adduct levels were found in the aromatic fractions and slightly polar fractions which contain most of the polycyclic aromatic hydrocarbons (PAH) and nitro-substituted PAH (nitro-PAH), respectively, comprising 75-90% of total adducts. This partitioning was independent of the sampling period and locality. In agreement with the higher average ambient air concentrations of PAH in the winter than the summer, 3-4-fold higher DNA adduct levels were detected in extracts sampled in the winter. Calculated on the basis of EOM/m(3), DNA adduct levels of samples collected in winter period were 10-fold higher than those collected in the summer period and 2-fold higher in Teplice than in Prachatice. Pretreatment of hepatocytes with 2,3,7,8-tetrachlorodibenzo-p-dioxin decreased DNA binding by 50-75%. In contrast to the findings in hepatocytes, in V79NH cells about 80% of the DNA adducts were caused by material in the slightly polar fractions appearing as distinct spots in the radiochromatograms. Seasonal variation of DNA adducts in V79NH cells was greater than variation between localities. Our results suggest that PAH as well as nitro-PAH are the main contributors to the genotoxicity of EOM derived from both industrial and rural areas. The results, furthermore, indicate that analysis of DNA adducts in mammalian cells in culture offers a suitable method for monitoring the genotoxicity of complex mixtures of environmental chemicals

Folk theorems on the correspondence between state-based and event-based systems

Kripke Structures and Labelled Transition Systems are the two most prominent semantic models used in concurrency theory. Both models are commonly believed to be equi-expressive. One can find many ad-hoc embeddings of one of these models into the other. We build upon the seminal work of De Nicola and Vaandrager that firmly established the correspondence between stuttering equivalence in Kripke Structures and divergence-sensitive branching bisimulation in Labelled Transition Systems. We show that their embeddings can also be used for a range of other equivalences of interest, such as strong bisimilarity, simulation equivalence, and trace equivalence. Furthermore, we extend the results by De Nicola and Vaandrager by showing that there are additional translations that allow one to use minimisation techniques in one semantic domain to obtain minimal representatives in the other semantic domain for these equivalences